Ultra thin lighting element

ABSTRACT

An ultra thin lighting element including at least one light source. A lightguide element includes one lightguide layer comprising a plurality of discrete fine optic surface relief structures on at least one portion of at least one surface. Each surface relief structure includes basic structural features on the order of about 10 microns or less in height, and on the order of about 10 microns or less in each lateral dimension. The number, arrangement and size of each surface relief structure and height and lateral dimensions of the structural features of the surface relief structures being varied to provide a desired degree of outcoupling modulation of light incoupled into the light guide element.

RELATED APPLICATIONS

This application claims priority from U.S. provisional application Ser.No. 60/566,601, filed Apr. 30, 2004.

FIELD OF THE INVENTION

The present invention relates to lightguides for guiding light fromlight sources in lighting solutions. The lightguides may include ultrathin lightguide layers and multi-layer applications. Additionally, thepresent invention includes lighting elements that include thelightguides and lighting solutions. The present invention also relatesto manufacturing methods. The lightguides and lighting elements can beused for display lighting (e.g. backlighting, frontlighting), interiorlighting and exterior lighting, among other applications.

SUMMARY OF THE INVENTION

An ultra thin lighting element is provided. The lighting elementsincludes at least one light source. A lightguide element includes onelightguide layer comprising a plurality of discrete fine optic surfacerelief structures on at least one portion of at least one surface. Eachsurface relief structure includes basic structural features on the orderof about 10 microns or less in height, and on the order of about 10microns or less in each lateral dimension. The number, arrangement andsize of each surface relief structure and height and lateral dimensionsof the structural features of the surface relief structures being variedto provide a desired degree of outcoupling modulation of light incoupledinto the light guide element.

Further objectives and advantages, as well as the structure and finctionof exemplary embodiments will become apparent from a consideration ofthe description, drawings, and examples.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following, more particular description of an exemplaryembodiment of the invention, as illustrated in the accompanying drawingswherein like reference numbers generally indicate identical,functionally similar, and/or structurally similar elements.

FIGS. 1 a and 1 b represent illustrations showing cross-sectional viewsof two embodiments of known lightguide structures;

FIGS. 2 a, 2 b, and 2 c represent illustrations showing cross-sectionalviews of various embodiments of ultrathin lighting elements according tothe present invention;

FIG. 3 represents an illustration showing a perspective view of anembodiment of an ultrathin lighting element according to the presentinvention;

FIGS. 4 a and 4 b represent illustrations showing cross-sectional viewsof embodiments of an ultrathin lighting elements according to thepresent invention including curved lightguide elements;

FIG. 5 a represents an illustration showing a cross-sectional view of anembodiment of a lighting element according to the present invention thatincludes a matrix including a plurality of lighting elements;

FIG. 5 b represents an illustration showing a cross-sectional view of anembodiment of a lighting elements according to the present inventionincluding a bendable lightguide element;

FIGS. 6 a, 6 b, 6 c, and 6 d represent illustrations showingcross-sectional views of embodiments of lighting elements according tothe present invention that include lightguide elements including twolightguide layers;

FIGS. 7 a, 7 b, and 7 c represent illustrations showing cross-sectionalviews of embodiments of lighting elements according to the presentinvention that include lightguide elements including two lightguidelayers and including various optical relief structures optionally onvarious surfaces on various surfaces and optionally various filmsarranged between the layers;

FIGS. 8 a, 8 b, and 8 c represent illustrations showing cross-sectionalviews of embodiments of lighting elements according to the presentinvention that include lightguide elements including two or morelightguide layers, optionally in various regions, and including variousoptical relief structures optionally on various surfaces on varioussurfaces and optionally various films arranged between the layers;

FIG. 9 a represents an illustration showing a cross-sectional view of anembodiment of a lighting element according to the present inventionwherein a portion of the lightguide element includes two lightguidelayers and a bendable lightguide layer;

FIGS. 9 b and 9 c represent illustrations showing cross-sectional viewsof embodiments of a lighting elements according to the present inventionthat include a single lightguide layer bent to form a two layerlightguide element;

FIGS. 10 a and 10 b represent illustrations showing overhead views ofembodiments of a lighting element according to the present invention;

FIG. 11 represents an illustration showing an overhead view of alighting element according to the present invention illustrating varioussizes that the embodiment of the lightguide element;

FIGS. 12 a, 12 b, and 13 represent illustrations showing overhead viewsof embodiments of lightguide elements according to the present inventionthat include various patterns of surface relief structures over thelightguide elements;

FIGS. 14 and 15 represent illustrations showing cross-sectional views ofembodiments for manufacturing lightguide layers according to the presentinvention utilizing roll-to-roll production;

FIG. 16 represents and illustration showing a cross-sectional view ofembodiments for manufacturing lightguide layers according to the presentinvention utilizing ultraviolet (UV) casting;

FIGS. 17 a, 17 b and 17 c represent illustrations showing overhead viewsof embodiments of lightguide layers according to the present invention;

FIG. 18 represents an illustration showing a cross-sectional view of anembodiment of a keypad including a lighting element according to thepresent invention;

FIGS. 19 a, 19 b, and 19 c represent illustrations showing variousembodiments of lightguide layers according to the present inventionincluding surface relief structures arranged in various groupings;

FIGS. 20 a and 20 b represent illustrations showing, respectively, anoverhead view and a side view of an embodiment of a lighting elementaccording to the present invention where the incoupling structureincludes optic fibers;

FIGS. 21 a and 21 b represent illustrations showing overhead views oflightguide elements according to the present invention including surfacerelief structures in different groupings in a region of the lightguidelayer in the vicinity of the light sources;

FIGS. 22 a and 22 b represent illustrations showing an overhead view anda cross-sectional view of an embodiment of a lightguide layer whereinthe basic structural features of the surface relief structures form asmall discrete outcoupling structure groups;

FIGS. 23 a and 23 b represent illustrations showing an overhead view anda cross-sectional view of an embodiment of a lightguide layer whereinthe different basic structural features of surface relief structures areforming small discrete outcoupling structure groups; and

FIGS. 24 a and 24 b represent illustrations showing cross-sectionalviews of various embodiments of basic structural features of surfacerelief structures according to the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Embodiments of the invention are discussed in detail below. Indescribing embodiments, specific terminology is employed for the sake ofclarity. However, the invention is not intended to be limited to thespecific terminology so selected. While specific exemplary embodimentsare discussed, it should be understood that this is done forillustration purposes only. A person skilled in the relevant art willrecognize that other components and configurations can be used withoutparting from the spirit and scope of the invention.

The present invention provided a lighting element that includes alightguide element. The lightguide element includes at least onelightguide layer. The lightguide layer(s) may be made of a variety ofdifferent materials. Typically, any optically clear material may beutilized. Examples of materials that may be utilized include PMMA, PC,PET and other polymers. The materials may be clear UV or thermal cured.

Circuitry, electrical contacts, printed figures or masks may be appliedon one or more lightguide layers.

The at least one lightguide layer includes a plurality of discrete fineoptic surface relief structure groups on at least one portion of atleast one surface. The surface relief structure group may be provided onat least a portion of each side of each lightguide layer. Each surfacerelief structure group is made up of basic structural features. Thestructural features can include (discrete or non-continuous) grooveshaving various cross-sections, such as different cross-sectional waveforms. The surface relief structures may include diffractive and/orrefractive structures. The structural features can have anycross-sectional shape such that they can outcouple light from thelightguide layer. The outcoupling from group to group may be the same,such as with a keypad. On the other hand, the outcoupling of each groupmay be different. It may even be desirable to vary the outcoupling ofone group at different locations in the group.

The structural features can have any cross-sectional shape such thatthey can outcouple light from the lightguide layer. For example, theoptic surface relief structure for light outcoupling is typically a finegrating structure. The grating profile can be binary, blazed, slantedand sinusoidal or hybrid, among other shapes. The light outcouplingstructure of lightguide layer can be designed in order to form uniformillumination on the whole surface or discrete illumination in thepreferred areas with preferred shape. The grating structures can beoptimised in order to achieve high outcoupling efficiency in 0° angle(collimated light) utilizing, for example, blazed type grating.

The surface relief structures may be arranged over the entire surface orsubstantially the entire surface of a lightguide layer. Alternatively,the surface relief structures may be confined to all of one region of alightguide layer. In some embodiments, the surface relief structures areconfined to certain regions of the at least one lightguide layer. Theregions may be regularly or irregularly arranged on any lightguidelayer. The desired degree of outcoupling may affect the arrangement ofthe surface relief structures. The proximity to the light source(s) mayalso affect the arrangement of the surface relief structures. Forexample, a region of the lightguide layer in the vicinity of the atleast one light source the outcoupling structure groups comprise about10% or less of the area of the lightguide layer.

Each surface relief structure includes basic structural features. Thedimensions of the basic features may depend upon the desired degree ofoutcoupling and the wavelengths of light being utilized. Typically, thebasic features are on the order of about 10 microns or less in height,and on the order of about 10 microns or less in each lateral dimension.More typically, the basic features are on the order of less than about10 microns in height, and on the order of less than about 10 microns ineach lateral dimension.

FIGS. 24 a and 24 b represent illustrations showing cross-sectionalviews of various embodiments of basic structural features of surfacerelief structures according to the present invention. These shapesrepresent only a few examples of the cross-sectional shapes that thebasic structural elements may have. Any lightguide layer may includeanyone or more of these shapes in any region of surface reliefstructures. To facilitate the understanding of these features, thefeatures are illustrated in a few discrete groups. As is apparent fromthe discussion herein, the surface relief structures may be providedanywhere on any lightguide layer.

The lightguide element may include more than one lightguide layer. Ifthe lighting element includes more than one lightguide layer, thelightguide layers may have the same cross-sectional area. Alternatively,the lightguide layers may have different cross-sectional areas. Thenumber of lightguide layers may vary over the lightguide element. Thethickness of the single lightguide layer may be about 0.01 mm to about0.4 mm. The lightguide element may have a thickness similar to theheight of the light source.

The entire lightguide element may be planar. At least a portion of oneor more of the lightguide element may be flexible and/or bendable. Thebend may be permanent or the lightguide element may be bent during use.The lightguide is flexible in the sense that light can still bepropagated through it and outcoupled out of it on either side of curveor bend. If the lightguide element includes more than one lightguidelayer, one or more the lightguide layers may be bendable and/orflexible. When at least a portion of the lightguide element is curved,the angle of the curve typically does not exceed a total reflectionangle.

If the lightguide element includes more than one lightguide layer, oneor more films may be arranged at least a portion of any region betweenoverlying two lightguide layers. A variety of different films may bearranged between lightguide layers. For example, the film can includeone or more of reflector film, diffuser film, prismatic film andbrightness enhancement film, in order to form different lightingperformances.

At least one light source produces light that is introduced into thelightguide element. The light source could include an LED or othersuitable light source. The light is incoupled into the lightguideelement. The light source could be connected directly to the lightguideelement and directly introduce light into the lightguide element.Alternatively, the lighting element may be arranged with one or moreincoupling structures. The incoupling structure may include a wedgeincluding specular reflectors on at least one of a top and bottomsurface, an elliptical light pipe, a focusing lens and/or a bundle ofsplit optic fibers. The light source and the incoupling structure may bea unitary structure. Where the lightguide element includes multiplelightguide layers, the incoupling may vary among the layers. Someembodiments of the incoupling structure may include a slanted, a blazedor a radial binary grating structure with or without diverging lens.

The present invention provides great advantages over known lightguidestructures, particularly in terms of providing a thin and flexiblestructure. For example, an ultra thin lightguide, which requires lessspace. This can be a very important issue especially in hand heldproducts such as mobile phones, watches, but also in other display,keypad, console and lighting solutions.

Embodiments of a thin, flexible lightguide according to the inventionthat can be bent can allow making interesting applications, such asflexible and/or curved displays, flexible phones, clam shell mobilephones (flip-phones). Embodiments of the present invention that includemultiple lightguide layers offer the ability to easily control lightincoupling/outcoupling and other optical performances, in each layer.Two or more lightguide layers can be stacked on top of another.Reflector and/or films can be utilized between these.

Light may be incoupled into the lightguide layers in proportion to layerthickness. Along these lines, thickness typically incouples less light,whereas more thickness typically incouples more light. This can providea very easy way to control the light incoupling and can also distributethe light to different lightguide layers. This concept is suitable fordual backlights, backlights with keypad lighting, dual backlights withkeypad lighting, among other structures.

The total thickness of the lightguide stack-up can be the same as theheight of the LED. For example, according to one embodiment, the LED hasa height of about 0.8 mm.

The present invention may include a centralized light sourcearrangement. This typically requires less light sources (e.g. LEDs),less assembly costs and less space. Embodiments of the present inventionthat include multi-layer lightguide layers can utilize light sourcesthat are placed on only one edge of the lightguide stack up. Alllightguide layers may propagate light to the right area, in order to beilluminated.

Embodiments of the present invention can provide practical variabilityin the size of the lightguide and the amount of light sources. This canprovide more flexibility to utilize the same lightguide design indifferent applications. The lightguide design may be formed for aspecific size with a specific optical diffusing structure or lightdirecting structure in the first (light incoupling) part, which is inthe vicinity of the light source(s), which is not dependent on preciselight source (e.g. LED) placement. This type of optical design can allowthe use of different amounts of light sources, while having the minimumquantity of light sources and maximum quantity of light sources on thesame edge. This can permit achieving higher or lower brightness with thesame uniformity performance. Additionally, the same lightguide designcan be cut to different sizes in order to achieve the same performancein uniformity.

The present invention can provide extremely cost-effective production.For example, the surface relief structure may be formed by means of acontinuous roll replication process (roll-to-roll process). This methodoffers extremely fast production, with high optical product quality.

Conventional thin lightguides typically have a thickness of about 0.8 toabout 1.0 mm and typically include microlens or microstructures. Suchconventional microstructures, such on the order of about 15 microns inheight or more, and on the order of about 50 microns or more in onelateral dimension, cannot be utilized in thin flexible lightguides for avariety of reasons. For example, these optical structures are unable tofunction properly with large incidence angles. Additionally, theseoptical structures have a limited degree of modulation, to achieveuniform light outcoupling distribution in thin lightguide solution.Furthermore, conventional production methods, such as injection molding,can cause problems with optical quality in thin lightguide solutions.

Preferred embodiments of the present invention can provide an ultra thinlightguide (film-like) solution with a single layer thickness of about0.4—about 0.01 mm. Embodiments of the present invention can includelightguides with single layer and multilayer solutions. All layers mayhave surface relief structures, which may be formed on the surface inorder to achieve different optical functions. These optical structurescan be diffractive and/or refractive having different profiles such asbinary, slanted, blazed, and sinusoidal, etc., forming different lightoutcoupling groups or sub-groups.

Multilayer lightguide elements according to the present invention mayhave a thickness that may be matched by the height of the light source.For example, if the light source includes an LED, the LED may have aheight of about 0.8 mm, the lightguide element may include multiplelightguide layers and a reflector arranged between the layers may have aheight of about 0.8 mm. The light incoupling and luminance (brightness)may be controlled by varying the thickness of each lightguide layer. Forexample, light from the light source may incoupled into the lightguidelayers in proportion to layer thickness. Along these lines, lessthickness=less light incoupling and less brightness, more thickness=morelight incoupling and more brightness. This is a very simple way tocontrol the light incoupling and distributes the light to the differentlightguide layers, permitting a controlled and desired brightness to berealized in each of the lightguide layers.

The lightguide layers according to the present invention may bemanufactured according to a number of different processes. Thinlightguide layer production is preferably completed by means ofcontinuous roll replication, or roll-to-roll replication. Using thisfast, cost-effective manufacturing method bulk material, such asoptically clear plastic film, can be utilized in surface reliefreplication. These different well know roll-to-roll methods are wellknown and well sophisticated to manufacture surface relief structures,either refractive or diffractive for many different applications. Thereare several published material and many companies having patentedroll-to-roll methods available, such as Reflexite, Avery Dennison, 3M,Epigem, Rolltronics, Polymicro, Printo project, among others.Additionally, high quality replicated optical structures can beachieved.

Other suitable production methods can include continuous or discretecasting methods (UV or thermal curing), compression molding, continuousor discrete embossing, such as hard embossing, soft embossing and UVembossing, among others. Melt film can also be used. Although manymanufacturing processes may be utilized, some may be particularlysuitable to manufacturing particular embodiments. For example, blazedtype structural profiles may be best manufactured by means ofroll-to-roll UV-embossing or a melt film method, in order to achieveaccurate and high quality replication.

Other functional films, such as reflector films, can be laminated ontothe surface of lightguide during the same roll-to-roll productionmethod. Also, any kind of figures and mask can be printed or laminatedon the lightguide layer including electrical contact and circuitries.This can be a crucial cost issue.

After the surface relief structures are formed, the lightguide layerscan be cut to preferred shapes directly from a roll or film by means oflaser, die cutting and/or other means. Also, optical features can bemanufactured during the cutting process. Such optical featuresparticularly include narrow boundary lines, which can be reflecting ordirecting light for the preferred area, or directing/diffusing light inthe first part of lightguide. This cutting process can be completed inthe roll-to-roll process with very short unit times and costs.

Injection molding as a production method may make it difficult tomanufacture ultra thin lightguides in sizes larger than about 10″/15″.The reason for this is that fine optic structures, such as surfacerelief structures on the order of about 15 microns and less, may bedifficult to replicate totally/perfectly and at the same time achieve ahigh quality yield.

The optical structure, or surface relief structure, of a thin lightguidetypically requires a high and increased degree of modulation to achievethe uniform light outcoupling distribution, or brightness. The opticalbasic structure typically must be very fine, such as on the order ofsmaller than about 10 microns or less in height, and on the order ofabout 10 microns or less in one lateral dimension, in order to achievethe desired degree of modulation. This makes it possible to form smalldiscrete outcoupling structure groups and control the proportion ofoutcoupling structures on the lightguide layer more accurately.Preferably, in thin lightguide layers, the optical structures arearranged in small discrete outcoupling structure groups, wherein aregion of the lightguide layer in the vicinity of the at least one lightsource the outcoupling structure groups comprise about 10% or less ofthe area of the lightguide layer. In this region the maximum distancebetween small discrete outcoupling structure groups is 300 microns orless. This region may be the most crucial part of the lightguidestructural design, because an intensity of incoupled light can be 50% ormore of maximum intensity.

Conventional microstructure solutions that are based on bigger andhigher optical details, typically have difficulties in thin lightguidesin order to achieve uniform brightness.

Embodiments of a lightguide element according to the present inventioncan be flexible. In some cases, less than all lightguide layers of alightguide element may be flexible. Embodiments of the inventionincluding a flexible lightguide element can be bent into a desired form.Such embodiments can be flexible and curved (bent) for preferred form inorder to fulfill total reflection theory and not exceeding the totalreflection angle.

A thin lightguide can help to prevent light leakage, because light beamstypically hit the optical structure more times than in a thickerlightguide. The total light can be outcoupled more efficiently, causingless light leakage at the end of the lightguide.

Ultra thin lightguides can be used as a single layer with or withoutother optic films (reflector, diffusers, brightness enhancement films).Thin lightguide layer can have fine optical structures, either on oneside or both sides of the layer.

In order to use only one lightguide layer, a conventional LED may beadapted to the lightguide layer with a specific optical component oradapter, which helps to incouple light into a thin lightguide layer. Forexample, the LED height may be 0.8 mm as compared to a lightguide layerhaving a thickness of about 0.2 mm. This LED optical component oradapter could be, for example, a wedge-type solution with specularreflectors on the top and bottom. Other incoupling structures that maybe utilized can include a thin elliptical light pipe, a focusing lens ora bundle of split optic fibers. Also, LEDs with circuitry can bein-molded into this adapter. This can make it easier to handle them.This adapter can contain snap structures in order to connect it to thelightguide layer easily. This adapter can be made of either rigid orflexible optical material. Process methods for forming the adapter canbe, for example, casting or injection molding. Light incoupling may becompleted with specific grating structures on the bottom or on the topsurface. For example, a slanted, a blazed or radial binary gratingstructure may be utilized with or without a diverging lens.

Ultra thin lightguide elements can be constructed with two or morelayers. Lightguide layers can form, for example, a dual backlightsolution, backlight and keypad lighting solution, dual backlight andkeypad lighting solution. For dual backlight solution, only onereflector film between lightguide layers may be required. This can cutcosts and makes the package thinner and easier to handle and assemble.In a solution that includes two layers, the optical outcouplingstructures can be arranged in the center line of the lightguide solution(inner surfaces of lightguide layers), because the major part ofincoupled light may be propagated along a center line. In the words, themajority of light may be propagated at high incidence angles.

One or more lightsources may be arranged to provide light that isintroduced into the lightguide element. According to some embodiments,all light sources can be placed on the one edge of a lightguide elementfor light incoupling into the lightguide layers. This centralized lightsource arrangement may reduce the amount of needed light sources andremove the need for a light source multi-assembly. This can have adirect influence on total cost reductions.

One preferred application is the backlight and keypad combination, wherea centralized LED arrangement can be used on the edge of lightguidestack up. The same LEDs can provide illumination for the backlight andkeypad. In conventional solutions separate LEDs for both the backlightand keypad illumination must be used.

The optical structure of the lightguide layer can be designed withvariation capabilities concerning its size and the amount of lightsources that it incorporates. The optical lightguide design in the firstpart (light incoupling part) of the lightguide structure can beoptimized in such a manner that the light from a point source, such asan LED, may be diffused at different conical angles or directedpartially at the same angle, in order to achieve more uniform and/ordirected light distribution in the first part. The optical design of thelightguide is not dependent on an exact light source placement. Thistype of optical design allows the use of different numbers of lightsources, having a minimum quantity of light sources and a maximumquantity of light sources on the same edge in order to achieve higherand lower brightness with same uniformity performance. This type ofoptic surface relief structure may be placed on the top and the bottomsurface of the first part of lightguide layer, having diffractive orrefractive grooves.

The outcoupling structure may be optimised a manner that it can allowcutting and using the same lightguide design in different sizes in orderachieve the same uniformity performance. This can make a lightguidesolution more variable and flexible to utilize it in different solutionsand applications, without the need to design many lightguide elements,which may have only slight differences in brightness and sizerequirements.

Conventional known keypad, keyboard and console lighting typicallyincludes 3-8 LEDs and a thick lightguide having holes for each keys orbuttons in order to make electrical contact. Such designs includeelectric circuitry with the help of dome sheet that includes pluralityof thin metal domes, one per each key or button. When pushing the key orthe button, the thin metal dome on the sheet is bent and flattenedmaking electrical contact, for example, on the surface of electriccircuitry. The dome also provides touch feeling with a click effect. Theholes are needed to make such designs function. However, these holesmake it difficult to manage light in order to achieve uniform keypadlighting.

On the other hand, an ultra thin lightguide layer according to thepresent invention can be used in keypad lighting, having a thickness ofabout 50 to about 200 microns, which provides a good flexible and touchsensitive performance, while retaining a click effect. As a result, thelightguide layer can be used without any holes for the keys and buttons.This makes light management easy in order to achieve uniform keypadlighting. Also, less LED components are needed, because the light can beoutcoupled more efficiently. This lightguide layer can be placed betweenbuttons and dome sheet and it requires much less space than conventionallightguide.

The dome sheet can be adapted/integrated on the lightguide element inorder to decrease amount of components required in a keyboard or keypad.Along these lines, electrical contacts and/or circuitries can beproivded on one or more lightguide layers making up a lightguideelement. These contacts and circuitries may be provided utilizing thelatest lamination and printing processes. For example, a roll-to-rollprocess may be utilized. In addition, optic surface relief structuresmay adapted/integrated on a keypad or keyboard component, or it can belaminated on the top of a printed circuit board. The buttons and keysmay be diffusing collimated light for larger illumination angle.

FIG. 1 a illustrates a conventional lightguide 2 a with an opticalsurface relief structure 3 a on at least one side of the whole surfacefor the light outcoupling. The conventional thin lightguide solution hasan even thickness of about 0.8 mm with the LED 1 a at the same height.

FIG. 1 b illustrates a conventional lightguide 2 b with an opticalsurface relief structure 3 b at least on one side of the whole surfacefor the light outcoupling. The conventional thin lightguide solution hasa thickness of about 0.6 mm with a light incoupling wedge for the higherLED 1 a.

FIG. 2 a illustrates an embodiment of an ultra thin lightguide element 2c according to the present invention with an optical surface reliefstructure 3 c on one side of the whole surface for the lightoutcoupling. The lightguide element includes one lightguide layer. Thisultra thin lightguide solution has a substantially even thicknesstypically about 0.25 to about 0.4 mm with the LED 1 b at the sameheight.

FIG. 2 b illustrates another embodiment of an ultra thin lightguideelement 2 d according to the present invention that includes an opticalsurface relief structure 3 d on both side of the whole surface for thelight outcoupling. This embodiment of an ultra thin lightguide has asubstantially even thickness, typically about 0.25 to about 0.4 mm withthe LED lb at the same height.

FIG. 2 c illustrates another embodiment of an ultra thin lightguideelement 2 e according to the present invention that includes an opticalsurface relief structure 3 e on one side of the surface for the discretelight outcoupling. This ultra thin lightguide solution has asubstantially even thickness, typically about 0.25 to about 0.4 mm withthe LED 1 b at the same height. This is a suitable solution for thekeypad or keyboard lighting.

FIG. 3 illustrates another embodiment of an ultra thin lightguideelement 2 f according to the present invention that includes an opticalsurface relief structure 3 f on at least one side of the whole surfacefor the light outcoupling. This ultra thin lightguide solution has asubstantially even thickness, typically about 0.25 to about 0.4 mm withan optical wedge type adapter 4 a for better light incoupling into thelightguide. Along these lines, the LED 1 c may have a height of about0.8 mm, while the lightguide element may have a thickness of about 0.2mm. This embodiment of an incoupling structure may include specularreflectors on the top and bottom, which can prevent any light loss andto improve incoupling efficiency.

FIG. 4 a illustrates an embodiment of a curved ultra thin lightguideelement 2 g according to the present invention that includes an opticalsurface relief structure 3 g on at least one side of the surface forlight outcoupling. This embodiment of an ultra thin lightguide can beflexible and curved into a preferred form in order to fulfill the totalreflection theory, and does not exceed the total reflection angle. Thisultra thin lightguide solution can utilize top view LEDs 1 d.

FIG. 4 b illustrates an embodiment of a double curved ultra thinlightguide element 2 h according to the present invention with anoptical surface relief structure 3 h on at least one side of the surfacefor light outcoupling. This ultra thin lightguide can be flexible andcurved into a preferred form in order to fulfill total reflectiontheory, and does not exceed the total reflection angle. This ultra thinlightguide solution may include at least two light incoupling surfacesutilizing top view LEDs 1 d.

FIG. 5 a illustrates an embodiment of an ultra thin flexible lightguideelement 2 i according to the present invention including an arrangementfor a larger matrix solution with an optical surface relief structure 3i on at least one side of the surface the light outcoupling. This matrixincludes several lightguide modules in order to form larger illuminatedactive area in at least one direction. This application may be suitablebacklight solution for a flat display, such as an LCD TV. This solutionmay include top view LEDs 1 e as a light source. Of course, other lightsources could be utilized and/or alternatively arranged, as may thelightguide elements be alternatively arranged.

FIG. 5 b illustrates an embodiment of a flexible ultra thin lightguideelement 2 j according to the present invention having two separateoptical surface relief structures 3 j at least a portion of twodifferent surfaces of the lightguide layer for light outcoupling. Thisultra thin lightguide is flexible and can be bent into a desired form.Typically, the bending is carried out in order to fulfill totalreflection theory and does not exceed the total reflection angle. Thisembodiment of an ultra thin lightguide solution can utilize, for exampletop view LEDs 1 d.

FIG. 6 a illustrates an embodiment of a multi-layer lightguide elementstack up Sa that is based on two lightguide layers 2′k and 2″k with anoptical surface relief structure 3 k on one side of both layers on thewhole surface for the light outcoupling. This lightguide solution hassubstantially even thickness typically about 0.4 to about 0.8 mm withthe LED 1 f at the same height.

FIG. 6 b illustrates another embodiment of a multi-layer lightguideelement stack up 5 b that includes two lightguide layers 2′ and 2″ withan optical surface relief structure 31 on one side of both layer on thewhole surface for the light outcoupling. This lightguide solution has asubstantially even thickness typically about 0.4 to about 0.8 mm withthe LED if at the same height.

FIG. 6 c illustrates an embodiment of a multi-layer lightguide elementstack up 5 c that is based on two lightguide layers 2′m and 2″m with anoptical surface relief structure 3′m and 3″m on both sides of bothlayers on the whole surface for the light outcoupling. This lightguidesolution has a substantially uniform thickness typically about 0.4 toabout 0.8 mm with the LED If at the same height.

FIG. 6 d illustrates an embodiment of a multi-layer dual lightguideelement stack up 5 d that includes two lightguide layers 2′k and 2″kwith an optical surface relief structure 3 k on both side of both layerson the whole surface for the light outcoupling. Between the lightguidelayers is placed one reflector film 6. This lightguide solution has asubstantially uniform thickness typically about 0.4 to about 0.8 mm withthe LED 1 f at the same height.

FIG. 7 a illustrates embodiments of the present invention that includedifferent multi-layer lightguide element stack ups 5 e, 5 f, and 5 gthat include two lightguide layers 2′k, 2″k, 2′l, 2″l, and 2′o, 2″o withan optical surface relief structure 3 k, 3 l, and 3 o on one side ofboth layers on the whole surface for the light outcoupling. Opticalsurface relief structure can be diffractive (binary or blaze) orrefractive.

FIG. 7 b illustrates embodiments of the present invention that includedifferent multi-layer lightguide element stack ups 5 h, 5 i, and 5 jthat are based on two lightguide layers 2′p, 2″p, 2′q, 2″q, and 2′r, 2″rwith optical surface relief structures 3′p, 3″p, 3′q, 3″q, and 3′r, 3″ron both sides of both layer on whole surface for the light outcoupling.Optical surface relief structure can be diffractive (binary or blaze) orrefractive.

FIG. 7 c illustrates embodiments of the present invention that includedifferent multi-layer lightguide element stack ups 5 k, 5 l, and 5 mthat include two lightguide layers 2′k, 2″k and 2′l, 2″l with an opticalsurface relief structure 3 k and 3 l on one side of both layers on thewhole surface for the light outcoupling. Between the lightguide layersis placed one reflector film 6 or another type of optical film asprismatic film 7. The optical surface relief structure can bediffractive (binary or blaze) or refractive.

FIG. 8 a illustrates embodiments of a multi-layer dual lightguideelement stack up that includes two lightguide layers 2′s and 2″s havingan optical surface relief structure 3 s on one side of both layers onthe whole surface for the light outcoupling. Between the lightguidelayers is arranged a reflector film 6. The light incoupling andbrightness may be controlled by differing thickness of lightguide layer,more thickness=more light, less thickness=less light. This lightguidesolution is suitable for dual display backlighting, which has asubstantially uniform thickness typically about 0.4 to about 0.8 mm withthe LED Ig at the same height.

FIG. 8 b illustrates embodiments of the present invention that include amulti-layer lightguide element stack up that includes two lightguidelayers 2′t and 2″t. The lightguide layers have different cross-sectionalareas. Optical surface relief structures 3′t and 3″t are provided on oneside of both layers for the light outcoupling. As can be seen in FIG. 8b, the relief structures are arranged in different regions on eachlightguide layer. For example, the lightguide layer 2′t includes arelief structure over most if not all of its surface. On the other hand,the lightguide layer 2″t includes relief structures in isolated regions.This embodiment could be utilized with a mobile phone that includes adisplay and a keypad. Between the lightguide layers is arranged areflector film 6. The light incoupling and brightness may be controlledby differing thickness of lightguide layer, more thickness=more light,less thickness=less light. This lightguide solution is suitable fordisplay backlighting and keypad lighting, which has a substantiallyuniform thickness typically about 0.4 to about 0.8 mm with the LED 1 gat the same height.

FIG. 8 c illustrates an embodiment of the present invention thatincludes a multi-layer lightguide element stack up that includes threelightguide layers 2′u, 2″u, and 2″u with optical surface reliefstructure 3′u and 3″u on one side of each layer for the lightoutcoupling. Between the lightguide layers may be arranged reflectorfilms 6. The light incoupling and brightness may be controlled bydiffering thickness of lightguide layer, more thickness=more light, lessthickness=less light. This lightguide solution may be suitable for dualdisplay backlighting and keypad lighting, which may have a substantiallyuniform thickness typically about 0.4-0.8 mm with the LED 1 g at thesame height.

FIG. 9 a illustrates an embodiment of the present invention thatincludes a flexible multi-layer dual lightguide element stack up thatincludes two lightguide layers 2′v and 2″v with optical surface reliefstructures 3′v and 3″v on at least a portion of a side of both layersfor the light outcoupling. Between the lightguide layers may be arrangeda reflector film 6. This lightguide solution is flexible and can be bentinto a preferred form in order to fulfill total reflection theory andtypically does not exceed total reflection angle. The light incouplingand brightness may be controlled by differing thickness of lightguidelayer, more thickness=more light, less thickness=less light. Thislightguide solution may be suitable for dual display backlighting, suchas in a clam shell mobile phone, or flip phone, and may have asubstantially uniform thickness, typically about 0.4 to about 0.8 mmwith the LED 1 h at the same height.

FIG. 9 b illustrates an embodiment of the present invention thatincludes a multi-layer lightguide element stack up that is based on onelightguide layer 2 w that includes optical surface relief structures 3 won one side of layer for the light outcoupling. The lightguide layer isfolded up in order to form complete lightguide stack up. As can be seenin FIG. 9 b, the surface that includes the surface relief structureswill contact itself This illustrates how the present invention canprovide a multilayer lightguide element with only one lightguide layer.This lightguide solution can prevent light leakage in the end oflightguide. The thickness is typically about 0.2 to about 0.8 mm withthe LED 1 i at the same height.

FIG. 9 c illustrates an embodiment of the present invention thatincludes a multi-layer lightguide element stack up that includes onelightguide layer 2 w with an optical surface relief structure 3 w on oneside of layer for the light outcoupling. The lightguide layer may befolded up in order to form complete lightguide stack up. Between thelightguide layers may be arranged a reflector film 6. This lightguidesolution can prevent light leakage in the end of lightguide. Thethickness may typically be about 0.2 to about 0.8 mm with the LED 1 ihaving substantially the height. The LED may be connected easily to thelightguide edge with specific adapter, where LED is in-molded.

FIG. 10 a illustrates an embodiment of an ultra thin lightguide element2 y that includes an optical surface relief structure 3 y on at leastone side of the whole surface for the light outcoupling. The opticaldesign 9, in the first part or light incoupling part in the vicinity ofthe light sources, may be optimized in such a manner that the light fromthe point source 1 j:1, 1 j:11, 1 j:111 is diffused at different conicalangles or directed partially at the same angle, in order to achieve moreuniform and/or directed light distribution in the first part and in thewhole active area divided for sectors 10:I, 10:II, 10:III per lightsource. The optic design 9 is placed on the top and the bottom surfaceof the first part of lightguide layer, having diffractive or refractivegrooves. This embodiment of a lightguide element may not be dependent onprecise light source placement. This type of optical design can allowthe use of different amounts of light sources, while having the minimumquantity of light sources and maximum quantity of light sources on thesame edge, in order to achieve higher or lower brightness with the sameuniformity performance.

FIG. 10 b illustrates an embodiment of an ultra thin lightguide 2 yaccording to the present invention including an optical surface reliefstructure 3 y on at least one side of the whole surface for the lightoutcoupling. The optical design 9, in the first part or light incouplingpart, of the lightguide structure, may be optimized in such a mannerthat the light from the point source 1 j:1, 1 j:11, 1 j:111, 1 j:IV, 1j:V is diffused at different conical angles or directed partially at thesame angle, in order to achieve more uniform and/or directed lightdistribution in the first part and in the whole active area (divided forsectors 10:I, 10:II, 10:III, 10:IV, 10:V per light source). The opticdesign 9 may be placed on the top and the bottom surface of the firstpart of lightguide layer, having diffractive or refractive grooves. Thislightguide type may not be dependent on precise light source placement.This type of optical design can allow the use of different amounts oflight sources, while having the minimum quantity of light sources andmaximum quantity of light sources on the same edge, in order to achievehigher or lower brightness with the same uniformity performance.

FIG. 11 illustrates an embodiment of an ultra thin lightguide 2 y havingan optical surface relief structure 3 y on at least one side of thewhole surface for the light outcoupling. The optical outcouplingstructure may be optimised with or without light incoupling structure 9,which can allow cutting and using the same lightguide design indifferent sizes 11 a, 11 b in order achieve the same uniformityperformance. This can make lightguide solutions more variable andflexible to utilise it in different solutions and applications, withoutthe need to design many lightguides, which have only slight differencesin brightness and size requirements.

FIG. 12 a illustrates an embodiment of an ultra thin lightguide 2 z:0, 2z:1 with different optical surface relief structures 3 z:0, 3 z: 1 on atleast one side of the whole surface in order to achieve different lightperformances such as light directing or collimating, diverging,polarizing, among others. The lightguide layer may be folded up in orderto form complete lightguide stack up. This solution provides moreperformances in one package.

FIG. 12 b illustrates an embodiment of an ultra thin lightguide element2 z:0, 2 z:1, 2 z:2 having different optical surface relief structures 3z:0, 3 z:1, 3 z:2 on at least one side of the whole surface in order toachieve different light performances such as light directing orcollimating, diverging, polarizing, among others. The lightguide layermay be folded up in order to form complete lightguide stack up. Thissolution can provide more performances in one package.

FIG. 13 illustrates an embodiment of an ultra thin lightguide 2 z:0, 2z:1, 2 z:2, 2 z:3, 2 z:4 with different an optical surface reliefstructures 3 z:0, 3 z:1, 3 z:2, 3 z:3, 3 z:4 on at least one side of thewhole surface in order to achieve different light performances such aslight directing or collimating, diverging, polarizing, among others. Thelightguide layer may be folded up in order to form complete lightguidestack up. This solution can provide more performances in one package.

FIG. 14 illustrates an embodiment of a process for ultra thin lightguidemanufacturing by means of continuous roll replication, also known asroll-to-roll. The material moves from roll 12 to roll 14. Using thisfast, cost-effective manufacturing method, bulk material 13, such asoptically clear plastic film, such as PMMA, PC, or PET, can bereplicated with a surface relief replicator 15 such as nickel coatedcylinder, drum, roll having an optical surface relief structure.

FIG. 15 illustrates another embodiment of a process for ultra thinlightguide manufacturing by means of continuous roll replication, alsoknown as roll-to-roll. The material moves from roll 12 to roll 14. Usingthis fast, cost-effective manufacturing method, bulk material 13, suchas optically clear plastic film, such as PMMA, PC, or PET, can bereplicated with a surface relief replicator 15 such as nickel coatedcylinder, drum, roll having an optical surface relief structure.Additionally, other functional film 18, such as reflector film, can belaminated onto the surface of lightguide from the roll 17 during thesame roll to roll production method. An extra pre-heating 16 may besuitable to utilize to achieve better lamination quality.

FIG. 16 illustrates an embodiment of a process for ultra thin lightguide21 manufacturing by means of UV-casting. Using this fast, cost-effectivemanufacturing method bulk material 21, such as optically clear plasticresin, can be UV-cured with UV-light source 19 through the top glass 20.An optical surface relief structure may be replicated in a mold 23 witha nickel plate 22 having a surface relief structure.

FIG. 17 a illustrates an embodiment of a lightguide structures that maybe utilized in regions of the lightguide element remote from lightsource(s). As shown in this exemplary embodiment, the surface relief mayinclude basic structural features, such as grooves and/or recessesarranged in different groups having different sizes, shapes,orientations, configurations. The characteristics of the surface reliefmay also vary. Along these lines, the filling factor, shape, size,profile, cross-section, and orientation, among other characteristics.The groups may or may not be arranged in repeating patterns. Each groupmay have any shape, such as a regular or irregular polygon. For example,the groups could be rectangular, triangular, square, trapezpoidal or anyother shape. The arrangment of the grooves and/or recesses may varywithin each sub-group, within each group, and/or over the entirestructure. The characteristics of the grooves and their arrangement mayvary be varied to vary the incoupling and/or outcoupling characteristicsof the structure. For example, the arrangement could maximize thediffraction efficiency. The arrangement could also make diffractionefficiency is a function of location. In the embodiment shown in FIG. 17a, the surface relief structure is arranged in groups 25. Each groupincludes a plurality of sub-groups 27 that each include basic structuralfeatures 26 on the order of about 10 microns or less in height, and onthe order of about 10 microns or less in each lateral dimension. Eachgroup and subgroup could have other configurations.

FIG. 17 b illustrates an embodiment of a lightguide layer in thevicinity of light source(s) according to the present invention. In theembodiment shown in FIG. 17 b, the surface relief structure is arrangedin groups 29 in a regular pattern.

FIG. 17 c illustrates an embodiment of a lightguide layer in thevicinity of light source(s) according to the present invention. In theembodiment shown in FIG. 17 c, the surface relief structures arearranged in groups 29 in a non-regular pattern.

FIG. 18 illustrates an embodiment of an ultra thin lightguide layer 2 afor keypad lighting. This embodiment of the lightguide element has athickness of about 50 to about 200 microns, which provides a goodflexible and touch sensitive performances retaining a click effect. Thelightguide layer is arranged placed between keypad 30 and dome sheet 32and utilize much less space than a conventional lightguide. Due to thethin and flexible nature of the lightguide layer, the keypad pressingcan make electrical contact between dome sheet and the circuit board 33.The discrete optic surface relief structure of light outcoupling 3 å ispreferable fine grating structure. The grating structures may beoptimized in order to achieve high outcoupling efficiency in 0° angle(collimated light). The keypad is diffusing collimated light for largerillumination angle.

FIG. 19 a illustrates an embodiment of an ultra thin lightguide layer2′ä for keypad lighting with the fine optic surface relief structures3′ä provided over the whole surface to form a uniform illuminating area.

FIG. 19 b illustrates an embodiment of an ultra thin lightguide layer 2″ä that may be utilized with for keypad lighting with the discrete fineoptic surface relief structures 3″ä forming uniform and discreteilluminating areas.

FIG. 19 c illustrates an embodiment of an ultra thin lightguide layer2′″ä for keypad lighting with the fine optic surface relief structures3′″ä and short boundary surface lines 34 produced by cutting process,which can be reflecting or directing light for the illuminating areas.

FIG. 20 a and 20 b illustrate, respectively, an overhead view and a sideview of an embodiment of a lighting element 2 ö with an improved lightincoupling using a bundle of split optic fibers 35 between light source1 k and the lightguide layer.

FIG. 21 a illustrates embodiment of an ultra thin lightguide element 2′âaccording to the present invention wherein the surface relief structuresare arranged in small discrete outcoupling structure groups 29, whereina region 36′ of the lightguide layer in the vicinity of the at least onelongitudinal light source 11 the outcoupling structure groups includeabout 10% or less of the area of the lightguide layer.

FIG. 21 b illustrates embodiment of an ultra thin lightguide element 2″âaccording to the present invention wherein the surface relief structuresare arranged in small discrete outcoupling structure groups 29, whereina region 36″ of the lightguide layer in the vicinity of the at least onepoint light source 1 m, the outcoupling structure groups include about10% or less of the area of the lightguide layer. The maximum distance Dbetween small discrete outcoupling structure groups is 300 microns orless.

FIG. 22 illustrates embodiment of small portion of ultra thin lightguidelayer 2 á wherein the basic structural features 26 of surface reliefstructures is forming a small discrete outcoupling structure group 29.

FIG. 23 illustrates embodiment of small portion of ultra thin lightguidelayer 2 ã wherein the different basic structural features 26 of surfacerelief structures are forming small discrete outcoupling structuregroups 29, wherein the number, arrangement and size of each surfacerelief structure and height and lateral dimensions of the structuralfeatures of the surface relief structures being varied to provide adesired degree of outcoupling modulation of light incoupled into thelight guide element.

The embodiments illustrated and discussed in this specification areintended only to teach those skilled in the art the best way known tothe inventors to make and use the invention. Nothing in thisspecification should be considered as limiting the scope of the presentinvention. All examples presented are representative and non-limiting.The above-described embodiments of the invention may be modified orvaried, without departing from the invention, as appreciated by thoseskilled in the art in light of the above teachings. It is therefore tobe understood that, within the scope of the claims and theirequivalents, the invention may be practiced otherwise than asspecifically described.

1. An ultra thin lighting element, comprising: at least one lightsource; and a lightguide element comprising one lightguide layercomprising a plurality of discrete groups of fine optic surface reliefstructures on at least one portion of at least one surface, eachdiscrete group comprising basic structural features on the order ofabout 10 microns or less in height, and on the order of about 10 micronsor less in each lateral dimension, wherein the number, arrangement andsize of each surface relief structure and height and lateral dimensionsof the structural features of the surface relief structures being variedto provide a desired degree of outcoupling modulation of light incoupledinto the light guide element.
 2. The ultra thin lighting elementaccording to claim 1, wherein the surface relief structures are arrangedin small discrete outcoupling structure groups, wherein a region of thelightguide layer in the vicinity of the at least one light source theoutcoupling structure groups comprise about 10% or less of the area ofthe lightguide layer.
 3. The ultra thin lighting element according toclaim 1, wherein at least a portion of the surface relief structures arearranged in a regular pattern.
 4. The ultra thin lighting elementaccording to claim 1, wherein at least a portion of the surface reliefstructures are arranged in an irregular pattern.
 5. The ultra thinlighting element according to claim 1, wherein the lightguide element isflexible.
 6. The ultra thin lighting element according to claim 1,wherein the lightguide element is foldable.
 7. The ultra thin lightingelement according to claim 1, the lightguide element is curved.
 8. Theultra thin lighting element according to claim 1, wherein the lightguideelements comprises a plurality of lightguide layers.
 9. The ultra thinlighting element according to claim 8, further comprising: at least onefilm arranged between at least a portion of overlying lightguide layers,the film including at least one of reflector film, diffuser film,prismatic film and brightness enhancement film.
 10. The ultra thinlighting element according to claim 8, further comprising: a displayarranged adjacent at least a portion of at least side of the lightguideelement.
 11. The ultra thin lighting element according to claim 8,further comprising: a keypad.
 12. The ultra thin lighting elementaccording to claim 1, wherein the at least one lightguide layer has athickness of about 0.01 mm to about 0.4 mm.
 13. The ultra thin lightingelement according to claim 1, wherein the lightguide element has athickness similar to the height of the light source.
 14. The ultra thinlighting element according to claim 1, wherein the lightguide elementcomprises a plurality of lightguide layers, and wherein not all of thelightguide layers have the same thickness.
 15. The ultra thin lightingelement according to claim 1, wherein the lightguide element comprises aplurality of lightguide layers, and wherein the number of lightguidelayers differs over the lightguide element.
 16. The ultra thin lightingelement according to claim 1, further comprising: an optic reliefstructure on at least a portion of at least one side of the at least onelightguide layer.
 17. The ultra thin lighting element according to claim1, further comprising: an incoupling structure operative to incouplelight from the light source into the lighting element, wherein theincoupling structure comprises a wedge comprising specular reflectors ona top and bottom surface, an elliptical light pipe, a focusing lens or abundle of split optic fibers.
 18. The ultra thin lighting elementaccording to claim 17, wherein the light source and the incouplingstructure comprise a unitary structure.
 19. The ultra thin lightingelement according to claim 1, comprising multiple lightguide layers,wherein incoupling varies among the layers.
 20. The ultra thin lightingelement according to claim 17, wherein the incoupling structurecomprises a slanted, a blazed or a radial binary grating structure anddiverging lens.
 21. The ultra thin lighting element according to claim1, comprising a plurality of light sources, wherein all light sourcesare arranged on one edge of the lightguide element.
 22. The ultra thinlighting element according to claim 1, wherein light is incoupled intothe lightguide element such that it diffuses into the at least one lightguide layer at different conical angles.
 23. The ultra thin lightingelement according to claim 1, further comprising: a keypad, wherein theat least one light source lights the lightguide element and the keypad.24. The ultra thin lighting element according to claim 23, wherein thelightguide is continuous over keys and buttons.
 25. The ultra thinlighting element according to claim 23, further comprising: a dome sheetand electric circuitry wherein the at least one light guide overliessubstantially the entire dome sheet.
 26. The ultra thin lighting elementaccording to claim 25, wherein applying pressure to the at least onelight guide layer actuates keys included in the keypad.
 27. The ultrathin lighting element according to claim 25, wherein the dome sheet isintegrated with the at least one light guide layer.
 28. The ultra thinlighting element according to claim 23, wherein electric circuitry isapplied to at least one of the at least one lightguide layer.
 29. Theultra thin lighting element according to claim 1, further comprising: akeyboard, wherein the at least one light source lights the lightguideelement and the keypad.
 30. The ultra thin lighting element according toclaim 1, wherein the at least one lightguide layer has a thickness ofabout 0.25 mm to about 0.4 mm.
 31. The ultra thin lighting elementaccording to claim 1, wherein at least a portion of each side of the atleast one light guide layer includes surface relief structures.
 32. Theultra thin lighting element according to claim 1, wherein at least aportion of the at least one lightguide layer is curved, and wherein anangle of the curve does not exceed a total reflection angle.
 33. Theultra thin lighting element according to claim 1, wherein the lightguideelement simultaneously outcouples light from two opposite sides.
 34. Theultra thin lighting element according to claim 1, wherein a thickness ofthe lightguide element is substantially uniform over its entire length.35. The ultra thin lighting element according to claim 1, wherein the atleast one lightguide layer comprises surface relief structures on atleast a portion of two surfaces.
 36. The ultra thin lighting elementaccording to claim 1, wherein the surface relief structures comprise atleast one of diffractive and refractive structures.
 37. The ultra thinlighting element according to claim 1, wherein the lightguide elementcomprises two lightguide layers, wherein the two lightguide layerscomprise one folded lightguide layer.
 38. The ultra thin lightingelement according to claim 1, comprising a plurality of laterallyadjacent lightguide elements.